1. Field of the Invention.
This invention relates to biomedical devices, and more specifically relates to a new polyurethane and an antithrombogenic medical device made therefrom.
2. Background of the Invention.
Extensive investigations have been undertaken over many years to find materials that will be biologically and chemically stable toward body fluids. This area of research has become increasingly important with the development of various objects and articles which can be in contact with blood or other body fluids, such as artificial organs, vascular grafts, probes, cannulas, catheters and the like.
Synthetic plastics have come to the fore as preferred materials for such articles. Polyurethanes in particular have many properties which make them attractive for fabrication of medical devices. They have excellent physical properties and are less thrombogenic than most other classes of polymers. Nevertheless, much effort has been directed to development of a truly nonthrombogenic polyurethane surface.
Thrombogenicity has conventionally been counteracted by the use of anticoagulants such as heparin. Various procedures for attachment of heparin to otherwise thrombogenic polymeric surfaces have been disclosed. Eriksson et al. in U.S. Pat. No. 3,634,123 discloses steeping a plastic surface sequentially in a solution of a cationic surface active agent and an aqueous solution of heparin to ionically bond the heparin. Improvements in the surface active agent-heparin coating method are described in U.S. Pat. No. 3,810,781 to Eriksson et al.
In U.S. Pat. Nos. 4,349,467 and 4,613,517 to Williams et al. and in U.S. Pat. No. 4,865,870 to Hu et al.
U.S. Pat. No. 4,521,564 to Solomon et al. discloses coating a polyurethane article with an amine-rich and covalently conjugating aldehyde-actuated heparin to the amino groups thereof.
In copending application Ser. No. 499,154 of common assignee herewith, a catheter made from a thermoplastic hydrophilic polyurethane having a polyethyleneoxide soft segment absorbs water and expands to a larger lumen size when contacted with an aqueous liquid and may include a bioactive agent and a radiopaque agent.
Ferruti et al. disclose the heparin binding capacity of crosslinked polyamidoamines prepared by reacting diamines with bis acryloylpiperazines (Biomaterials, 218 (1983)). Azzuoli et al. in Biomaterials 8, 61 (1987), disclose an antithrombogenic polyurethane graft copolymer. A polyurethane or polyurethaneurea base layer is coated with a diisocyante and the diisocyante coating reacted with the polyamidoamine of Ferruti supra. The grafted polyamidoamine is protonated and treated with a heparin salt.
While significant advances have been made toward antithrombogenic surfaces for fabrication of medical devices, further improvements are needed. In particular, materials having surfaces that are essentially nonthrombogenic for use in devices which will be in contact with blood for prolonged periods are needed. It is toward fulfillment of this need that this invention is directed.